pgrag — EXPERIMENTAL

Experimental Postgres extensions to support end-to-end Retrieval-Augmented Generation (RAG) pipelines.

These currently provide:

Text extraction and conversion

• Simple text extraction from PDF documents using pdf-extract. Currently no OCR, and no support for complex layout or formatting.

• Simple text extraction from .docx documents using docx-rs (docx-rust). Currently no support for complex layout or formatting.

• HTML conversion to Markdown using htmd.

Text chunking

• Text chunking by character count using text-splitter.

• Text chunking by token count, again using text-splitter.

Local embedding and reranking models

These are packaged as separate extensions, because they are large (>100MB) and because we may want to add others in future.

• Local tokenising + embedding generation with 33M parameter model bge-small-en-v1.5 using fastembed.

• Local tokenising + reranking with 33M parameter model jina-reranker-v1-tiny-en using fastembed.

Remote embedding and chat models

• Querying OpenAI API for embeddings (e.g. text-embedding-3-small) and chat completions (e.g. gpt-4o-mini).

• Querying Fireworks.ai API for chat completions (e.g. llama-v3p1-8b-instruct).

Installation

First, you'll need to install pgvector. For example:

wget https://github.com/pgvector/pgvector/archive/refs/tags/v0.7.4.tar.gz -O pgvector-0.7.4.tar.gz
tar xzf pgvector-0.7.4.tar.gz
cd pgvector-0.7.4
export PG_CONFIG=/path/to/pg_config  # not just a path: should actually end with `pg_config`
make
make install  # may need sudo

Next, download the extensions source, and (if you are building the embedding or reranking extensions) extract the relevant model files:

cd lib/bge_small_en_v15 && tar xzf model.onnx.tar.gz && cd ../..
cd lib/jina_reranker_v1_tiny_en && tar xzf model.onnx.tar.gz && cd ../..

Then (with up-to-date Rust installed):

cargo install --locked cargo-pgrx@0.12.6

Finally, inside each of the three folders inside exts:

PG_CONFIG=/path/to/pg_config cargo pgrx install --release

The extension has been tested on Linux and macOS. It does not currently support Windows.

Embedding and reranking extensions

Background worker process

To avoid requiring excessive memory when reranking or generating embeddings in multiple Postgres processes, each of these tasks is done by a multi-threaded background worker (the worker is started when Postgres starts, but the models are lazy-loaded on first use).

For rag_bge_small_en_v15 and rag_jina_reranker_v1_tiny_en, you'll therefore need to edit postgresql.conf to add a shared_preload_libraries configuration:

shared_preload_libraries = 'rag_bge_small_en_v15.so,rag_jina_reranker_v1_tiny_en.so'

On macOS, replace .so with .dylib in these library names.

When using cargo pgrx run with Postgres instances installed by pgrx, postgresql.conf is located in ~/.pgrx/data-N (where N is the relevant Postgres version).

When using cargo pgrx test, postgresql.conf is inside the target directory of your extension, e.g. ~/path/to/myext/target/test-pgdata/N (where N is the relevant Postgres version).

ORT and ONNX installation

The ort and ort-sys crates are currently supplied in patched form in vendor while awaiting a 2.0.0-rc.9 release that fixes a build issue.

The ort package supplies precompiled binaries for the ONNX runtime (currently v1.19). On some platforms, this may give rise to undefined symbol errors. In that case, you'll need to compile the ONNX runtime yourself and provide the build location to cargo pgrx install in the ORT_LIB_LOCATION environment variable. An example for Ubuntu 24.04 is provided in COMPILE.sh.

Remote ONNX model file

By default, the embedding and reranking models are embedded within the extension (using Rust's include_bytes!() macro). But it's also possible to have these .onnx files downloaded on first use. This is enabled by the remote_onnx crate feature, and the download URL is specified via the REMOTE_ONNX_URL build-time environment variable. For example:

REMOTE_ONNX_URL=http://example.com/path/model.onnx cargo pgrx install --release --features remote_onnx

REMOTE_ONNX_URL defaults to a HuggingFace URL, but it is recommended to change this to a location you control.

Usage

create extension if not exists rag cascade;  -- `cascade` installs pgvector dependency
create extension if not exists rag_bge_small_en_v15 cascade; 
create extension if not exists rag_jina_reranker_v1_tiny_en cascade; 

markdown_from_html(text) -> text

Locally convert HTML to Markdown:

select rag.markdown_from_html('<html><body><h1>Title</h1><p>A <i>very</i> short paragraph</p><p>Another paragraph</p></body></html>');
--  '# Title\n\nA _very_ short paragraph\n\nAnother paragraph'

text_from_pdf(bytea) -> text

Locally extract text from a PDF:

\set contents `base64 < /path/to/your.pdf`
select rag.text_from_pdf(decode(:'contents', 'base64'));
-- 'Text content of PDF'

text_from_docx(bytea) -> text

Locally extract text from a .docx file:

\set contents `base64 < /path/to/your.docx`
select rag.text_from_docx(decode(:'contents', 'base64'));
-- 'Text content of .docx'

chunks_by_character_count(text, max_characters integer, max_overlap_characters integer) -> text[]

Locally chunk text using character count, with max and overlap:

select rag.chunks_by_character_count('The quick brown fox jumps over the lazy dog', 20, 4);
-- {"The quick brown fox","fox jumps over the","the lazy dog"}

chunks_by_token_count(text, max_tokens integer, max_overlap_tokens integer) -> text[]

Locally chunk text using token count for specific embedding model, with max and overlap:

select rag_bge_small_en_v15.chunks_by_token_count('The quick brown fox jumps over the lazy dog', 4, 1);
-- {"The quick brown fox","fox jumps over the","the lazy dog"}

embedding_for_passage(text) -> vector(384) and embedding_for_query(text) -> vector(384)

Locally tokenize + generate embeddings using a small (33M param) model:

select rag_bge_small_en_v15.embedding_for_passage('The quick brown fox jumps over the lazy dog');
-- [-0.1047543,-0.02242211,-0.0126493685, ...]
select rag_bge_small_en_v15.embedding_for_query('What did the quick brown fox jump over?');
-- [-0.09328926,-0.030567117,-0.027558783, ...]

rerank_distance(text, text) -> real

Locally tokenize + rerank original texts using a small (33M param) model:

select rag_jina_reranker_v1_tiny_en.rerank_distance('The quick brown fox jumps over the lazy dog', 'What did the quick brown fox jump over?');
-- -1.1093962

select rag_jina_reranker_v1_tiny_en.rerank_distance('The quick brown fox jumps over the lazy dog', 'Never Eat Shredded Wheat');
-- 1.4725753

openai_set_api_key(text) and openai_get_api_key() -> text

Store and retrieve your OpenAI API key:

select rag.openai_set_api_key('sk-proj-...');
select rag.openai_get_api_key();
-- 'sk-proj-...'

openai_text_embedding_3_small(text) -> vector(1536), openai_text_embedding_3_large(text) -> vector(3072), openai_text_embedding_ada_002(text) -> vector(1536), and openai_text_embedding(model text, text) -> vector

Call out to OpenAI embeddings API (makes network request):

select rag.openai_text_embedding_3_small('The quick brown fox jumps over the lazy dog');
-- {-0.020836005,-0.016921125,-0.00450666, ...}

openai_chat_completion(json) -> json

Call out to OpenAI chat/completions API (makes network request):

select rag.openai_chat_completion('{"model":"gpt-4o-mini","messages":[{"role":"system","content":"you are a helpful assistant"},{"role":"user","content":"hi!"}]}');
-- {"id": "chatcmpl-...", "model": "gpt-4o-mini-2024-07-18", "usage": {"total_tokens": 27, "prompt_tokens": 18, "completion_tokens": 9}, "object": "chat.completion", "choices": [{"index": 0, "message": {"role": "assistant", "content": "Hello! How can I assist you today?", "refusal": null}, "logprobs": null, "finish_reason": "stop"}], "created": 1724765541, "system_fingerprint": "fp_..."}

fireworks_set_api_key(text) and fireworks_get_api_key() -> text

Store and retrieve your Fireworks.ai API key:

select rag.fireworks_set_api_key('fw_...');
select rag.fireworks_get_api_key();
-- 'fw_...'

fireworks_chat_completion(json) -> json

Call out to Fireworks.ai chat/completions API (makes network request):

select rag.fireworks_chat_completion('{"model":"accounts/fireworks/models/llama-v3p1-8b-instruct","messages":[{"role":"system","content":"you are a helpful assistant"},{"role":"user","content":"hi!"}]}');
--  {"choices":[{"finish_reason":"stop","index":0,"message":{"content":"Hi! How can I assist you today?","role":"assistant"}}],"created":1725362940,"id":"...","model":"accounts/fireworks/models/llama-v3p1-8b-instruct","object":"chat.completion","usage":{"completion_tokens":10,"prompt_tokens":23,"total_tokens":33}}

End-to-end RAG example

Setup: create a docs table and ingest some PDF documents as text.

drop table docs cascade;
create table docs
( id int primary key generated always as identity
, name text not null
, fulltext text not null
);

\set contents `base64 < /path/to/first.pdf`
insert into docs (name, fulltext)
values ('first.pdf', rag.text_from_pdf(decode(:'contents','base64')));

\set contents `base64 < /path/to/second.pdf`
insert into docs (name, fulltext)
values ('second.pdf', rag.text_from_pdf(decode(:'contents','base64')));

\set contents `base64 < /path/to/third.pdf`
insert into docs (name, fulltext)
values ('third.pdf', rag.text_from_pdf(decode(:'contents','base64'))));

Now we create an embeddings table, chunk the text, and generate embeddings for the chunks (this is all done locally).

drop table embeddings;
create table embeddings
( id int primary key generated always as identity
, doc_id int not null references docs(id)
, chunk text not null
, embedding vector(384) not null
);

create index on embeddings using hnsw (embedding vector_cosine_ops);

with chunks as (
  select id, unnest(rag_bge_small_en_v15.chunks_by_token_count(fulltext, 192, 8)) as chunk
  from docs
)
insert into embeddings (doc_id, chunk, embedding) (
  select id, chunk, rag_bge_small_en_v15.embedding_for_passage(chunk) from chunks
);

Let's query the embeddings and rerank the results (still all done locally).

\set query 'what is [...]? how does it work?'

with ranked as (
  select
    id, doc_id, chunk, embedding <=> rag_bge_small_en_v15.embedding_for_query(:'query') as cosine_distance
  from embeddings
  order by cosine_distance
  limit 10
)
select *, rag_jina_reranker_v1_tiny_en.rerank_distance(:'query', chunk)
from ranked
order by rerank_distance;

Building on that, now we can also feed the query and top chunks to remote ChatGPT to complete the RAG pipeline.

\set query 'what is [...]? how does it work?'

with ranked as (
  select
    id, doc_id, chunk, embedding <=> rag_bge_small_en_v15.embedding_for_query(:'query') as cosine_distance
  from embeddings
  order by cosine_distance
  limit 10
),
reranked as (
  select *, rag_jina_reranker_v1_tiny_en.rerank_distance(:'query', chunk)
  from ranked
  order by rerank_distance limit 5
)
select rag.openai_chat_completion(json_object(
  'model': 'gpt-4o-mini',
  'messages': json_array(
    json_object(
      'role': 'system',
      'content': E'The user is [...].\n\nTry to answer the user''s QUESTION using only the provided CONTEXT.\n\nThe CONTEXT represents extracts from [...] which have been selected as most relevant to this question.\n\nIf the context is not relevant or complete enough to confidently answer the question, your best response is: "I''m afraid I don''t have the information to answer that question".'
    ),
    json_object(
      'role': 'user',
      'content': E'# CONTEXT\n\n```\n' || string_agg(chunk, E'\n\n') || E'\n```\n\n# QUESTION\n\n```\n' || :'query' || E'```'
    )
  )
)) -> 'choices' -> 0 -> 'message' -> 'content' as answer
from reranked;

License

This software is released under the Apache 2.0 license. Third-party code and data are provided under their respective licenses.